Solve the Problem $f ( x ) = 300 ( 0.5 ) ^ { x / 100 }$

Multiple Choice

Solve the problem.
-The function $f ( x ) = 300 ( 0.5 ) ^ { x / 100 }$ models the amount in pounds of a particular radioactive material stored in a concrete vault, where $x$ is the number of years since the material was put into the vault. Find the amount of radioactive material in the vault after 120 years. Round to the nearest whole number.

A) 131 pounds
B) 168 pounds
C) 180 pounds
D) 125 pounds